1. Explaining the 2001-02 Infant Mortality Increase Marian MacDorman, Joyce Martin, T.J.Mathews, Donna Hoyert, and Stephanie Ventura Division of Vital Statistics National Center for Health Statistics Centers for Disease Control and Prevention

2. Infant Mortality Rate: United States, 1990-2002 SOURCE: National Vital Statistics System, NCHS, CDC. +3%

3. Infant Deaths and Infant, Neonatal, and Postneonatal Mortality Rates: US, 2001-02 [Rates per 1,000 live births] Infant mortality rate Infant deaths Neonatal (Under 28 days) Postneonatal (28 days – 11 months) YearTotal Under 7 days 7-27 days 200227,9707.04.73.70.92.3 200127,5236.84.53.60.92.3 SOURCE: National Vital Statistics System, NCHS, CDC.

4. Infant Mortality Rates by Maternal Race and Ethnicity: United States, 2001 and 2002 SOURCE: National Vital Statistics System, NCHS, CDC 2001 2002

5. Infant Mortality Rates by Leading Causes: United States, 2001-02 Cause of death (ICD-10)20022001 Congenital anomalies144.0137.6 Short gestation/low birthweight115.3109.5 Sudden infant death syndrome57.155.5 Maternal complications of pregnancy42.437.3 [Rates per 100,000 live births ] NOTE: Bold, underlined numbers indicate a statistically significant increase from the previous year. SOURCE: National Vital Statistics System, NCHS, CDC.

6. Infant Mortality Rates by Birthweight: United States, 2002 grams

7. Percent of Births and Infant Deaths by Birthweight, United States, 2002 SOURCE: National Vital Statistics System, NCHS, CDC

8. Components of Infant Mortality The distribution of births by birthweight. Birthweight-specific infant mortality rates (the mortality rate for infants at a given weight)

9. Number of Live Births at <750 grams, United States, 2001 and 2002 Birthweight in grams +5% +2% +3% SOURCE: National Vital Statistics System, NCHS, CDC

10. Infant Mortality Rates by Birthweight, United States, 2001 and 2002 Birthweight in grams SOURCE: National Vital Statistics System, NCHS, CDC

11. Direct Standardization Used to measure the proportion of the overall 2001- 2002 infant mortality increase due to a change in: - The distribution of births by birthweight (98%) - Birthweight-specific infant mortality rates (2%)

12. Results by Period of Gestation Increase in the number and percent of extremely preterm births (<28 weeks) Significant increase in infant mortality rates for preterm (<37 weeks) and very preterm (<32 weeks) Direct Standardization indicated that: 61% of the increase was due to a change in the distribution of births by gestational age. 39% due to a change in gestational age-specific infant mortality rates.

13. Contribution of Multiple Births to 2001-02 Infant Mortality Increase Number of multiple births increased by: - 3% overall - 4% for <750 gram births Changes for multiple births accounted for ¼ of the overall infant mortality increase ¾ was due to changes for single births

14. Possible Factors that Might Explain the Increase in <750 Gram Births Changes in reporting of births and/or fetal deaths. Changes in the risk profile of births. Changes in medical management of pregnancy.

15. The Potential Influence of Reporting Changes

16. Percent of Live Births and Fetal Deaths 20+ Weeks, by Birthweight: US, 2001-02 SOURCE: National Vital Statistics System, NCHS, CDC Live Births 0.419 0.432 47.8 48.6 Fetal deaths 20+ weeks

17. Percent of Fetal Deaths 20+ Weeks that Occur at 20-27 Weeks: States Reporting All Periods of Gestation and All Other States, Selected Years 22% gap 18% gap 17% gap14% gap SOURCE: National Vital Statistics System, NCHS, CDC

18. The Potential Influence of Changes in the Risk Profile of Births

19. Increases in <750 gram births were: - concentrated mostly among 20-34 year old mothers - occurred for non-Hispanic white, non- Hispanic black, and Hispanic mothers

20. The Potential Influence of Changes in Medical Management of Pregnancy

21. Distribution of Births by Gestational Age: United States, 1990 and 2002 SOURCE: National Vital Statistics System, NCHS, CDC

22. Percent of Births with Induction of Labor by Gestational Age: U.S., 1990-2002

23. Percent of Births Delivered by Cesarean by Gestational Age: United States, 1990-2002

24. Conclusions 2001-2002 infant mortality increase: Due almost entirely to an increase in <750 gram births ¾ of the increase among singletons increase mostly for women aged 20-34

25. Conclusions (cont.) 2003 preliminary infant mortality rate is 6.9 Not significantly different from 2002 rate of 7.0 Preventing very preterm and very low birthweight deliveries is key to further lowering the US infant mortality rate.